革新プロ温暖化実験データによる梅雨期の降水の将来変化

Abstract

This study focuses on atmospheric circulation fields during the baiu in Japan with global warming projection experimental data conducted using a 20-km-mesh global atmospheric model (MRI-AGCM3.2S). The baiu front indicated by the north-south gradient of moist static energy moves northward, both in present and future climate simulations. The rate of progression is very slow in May and June. Particularly in the future climate, the baiu front stagnates in south of Japan, including the Okinawa region. In addition, then northward shift in July is associated with the westward expansion of the enhanced north Pacific subtropical high into Japan region. The horizontal warm advection roughly at the mid-troposphere corresponds to upward vertical pressure velocity, and shows northward migration as seen in the lower troposphere. The future change in these variables, about 5-day move north is delayed compared to the present-day climate. This tendency is evident in the north-south term of 500-hPa warm advection in particular. In conclusion, a late of the baiu rainfall band northward and an increase in precipitation during late of the baiu season are apparent from the point of view of atmospheric fields.